// inner variables
var canvas, ctx;
var button;
var backgroundImage;
var spaceShip;
var iBgShiftX = 1024;
var bDrawDialog = true;
var iDialogPage = 1;
// -------------------------------------------------------------

// objects :
function Button(x, y, w, h, state, image) {
  this.x = x;
  this.y = y;
  this.w = w;
  this.h = h;
  this.state = state;
  this.imageShift = 0;
  this.image = image;
}
function SpaceShip(x, y, w, h, image) {
  this.x = x;
  this.y = y;
  this.w = w;
  this.h = h;
  this.image = image;
  this.bDrag = false;
}
// -------------------------------------------------------------

// draw functions :

function clear() { // clear canvas function
  ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height);
}

function drawDialog() { // draw dialog function
  if (bDrawDialog) {
    var bg_gradient = ctx.createLinearGradient(0, 200, 0, 400);
    bg_gradient.addColorStop(0.0, 'rgba(160, 160, 160, 0.8)');
    bg_gradient.addColorStop(1.0, 'rgba(250, 250, 250, 0.8)');

    ctx.beginPath(); // custom shape begin
    ctx.fillStyle = bg_gradient;
    ctx.moveTo(100, 100);
    ctx.lineTo(700, 100);
    ctx.lineTo(700, 500);
    ctx.lineTo(100, 500);
    ctx.lineTo(100, 100);
    ctx.closePath(); // custom shape end
    ctx.fill(); // fill custom shape

    ctx.lineWidth = 2;
    ctx.strokeStyle = 'rgba(128, 128, 128, 0.5)';
    ctx.stroke(); // draw border

    // draw the title text
    ctx.font = '42px DS-Digital';
    ctx.textAlign = 'center';
    ctx.textBaseline = 'top';
    ctx.shadowColor = '#000';
    ctx.shadowOffsetX = 2;
    ctx.shadowOffsetY = 2;
    ctx.shadowBlur = 2;
    ctx.fillStyle = '#fff';
    if (iDialogPage == 1) {
      ctx.fillText('Welcome to lesson #3', ctx.canvas.width/2, 150);
      ctx.font = '24px DS-Digital';
      ctx.fillText('After closing dialog you will able', ctx.canvas.width/2, 250);
      ctx.fillText('to handle with spaceship with your mouse', ctx.canvas.width/2, 280);
    } else if (iDialogPage == 2) {
      ctx.fillText('Second page of dialog', ctx.canvas.width/2, 150);
      ctx.font = '24px DS-Digital';
      ctx.fillText('Any another text', ctx.canvas.width/2, 250);
    }
  }
}

function drawScene() { // main drawScene function
  clear(); // clear canvas

  // draw background
  iBgShiftX -= 10;
  if (iBgShiftX <= 0) {
    iBgShiftX = 1024;
  }
  ctx.drawImage(backgroundImage, 0 + iBgShiftX, 0, 1024, 768, 0, 0, 800, 600);

  // draw space ship
  ctx.drawImage(spaceShip.image, 0, 0, spaceShip.w, spaceShip.h, spaceShip.x-128, spaceShip.y-128, spaceShip.w, spaceShip.h);

  // draw dialog
  drawDialog();

  // draw button
  ctx.drawImage(button.image, 0, button.imageShift, button.w, button.h, button.x, button.y, button.w, button.h);

  // draw button's text
  ctx.font = '22px DS-Digital';
  ctx.fillStyle = '#ffffff';
  ctx.fillText('next/hide/show', 400, 465);
  ctx.fillText('dialog', 400, 500);
}

// -------------------------------------------------------------

// initialization
$(function(){
  canvas = document.getElementById('scene');
  ctx = canvas.getContext('2d');

  var width = canvas.width;
  var height = canvas.height;

  // load background image
  backgroundImage = new Image();
  backgroundImage.src = 'images/stars.jpg';
  backgroundImage.onload = function() {
  }
  backgroundImage.onerror = function() {
    console.log('Error loading the background image.');
  }

  // initialization of space ship
  var oSpShipImage = new Image();
  oSpShipImage.src = 'images/space_ship.png';
  oSpShipImage.onload = function() {
  }
  spaceShip = new SpaceShip(400, 300, 256, 256, oSpShipImage);

  // load the button sprite image
  var buttonImage = new Image();
  buttonImage.src = 'images/button.png';
  buttonImage.onload = function() {
  }
  button = new Button(310, 450, 180, 120, 'normal', buttonImage);

  $('#scene').mousedown(function(e) { // binding mousedown event (for dragging)

    var mouseX = e.layerX || 0;
    var mouseY = e.layerY || 0;

    if (!bDrawDialog && 
      mouseX > spaceShip.x-128 && mouseX < spaceShip.x-128+spaceShip.w &&
      mouseY > spaceShip.y-128 && mouseY < spaceShip.y-128+spaceShip.h) {

      spaceShip.bDrag = true;
      spaceShip.x = mouseX;
      spaceShip.y = mouseY;
    }

    // button behavior
    if (mouseX > button.x && mouseX < button.x+button.w && mouseY > button.y && mouseY < button.y+button.h) {
      button.state = 'pressed';
      button.imageShift = 262;
    }
  });

  $('#scene').mousemove(function(e) { // binding mousemove event
    var mouseX = e.layerX || 0;
    var mouseY = e.layerY || 0;

    if (!bDrawDialog && spaceShip.bDrag) {
      spaceShip.x = mouseX;
      spaceShip.y = mouseY;
    }

    // button behavior
    if (button.state != 'pressed') {
      button.state = 'normal';
      button.imageShift = 0;
      if (mouseX > button.x && mouseX < button.x+button.w && mouseY > button.y && mouseY < button.y+button.h) {
        button.state = 'hover';
        button.imageShift = 131;
      }
    }
  });

  $('#scene').mouseup(function(e) { // binding mouseup event
    spaceShip.bDrag = false;

    // button behavior
    if (button.state == 'pressed') {
      if (iDialogPage == 0) {
        iDialogPage++;
        bDrawDialog = !bDrawDialog;
      } else if (iDialogPage == 2) {
        iDialogPage = 0;
        bDrawDialog = !bDrawDialog;
      } else {
        iDialogPage++;
      }
    }
    button.state = 'normal';
    button.imageShift = 0;
  });

  setInterval(drawScene, 30); // loop drawScene
});